In a manufacturing plant of semiconductor, variety of metal hydride gases and halide gases are used during the manufacturing process. Since these gases are combustible and/or harmful, it is not allowed for environmental conservation to emit exhaust gas containing these gases to the atmosphere, therefore treatment for eliminating risky and hazardous properties thereof is needed.
As to the treatment for the exhaust gas, there are a wet type processing and a dry type processing. The former is a method of cleaning the exhaust gas with chemicals. While the latter is a method of circulating the exhaust gas into a filled column of a granular solid treating agent and thereby separating risky and hazardous gases and eliminating the harmful properties due to chemical functioning of gases targeted for harm elimination and the treating agent, for instance, adsorption and/or chemical reaction, and the method has often been used for treatment of metal hydride-containing exhaust gases or halide gas-containing exhaust gases.
A large number of patents are directed to the treating agents for metal hydride-containing exhaust gases. For examples, treating agents comprising metal hydroxide, metal carbonate, or basic metal carbonate are disclosed in Japanese laid-open patent publication No. 05-284847, Japanese laid-open patent publication No. 06-319945, Japanese laid-open patent publication No. 08-192024, Japanese patent publication No. 05-61966, registered Japanese patent publication No. 2604991 and the like.
These treating agents however have superior harm-eliminating capacities even if metal hydroxide, metal carbonate, or basic metal carbonate is independently used as a treating agent, but as rate of reaction is slow, in the case that a concentration level of harmful components in the exhaust gases is high or in the case that a flow rate thereof is high, a rate of harm-elimination is not enough, thereby the concentration level of harmful components therein after treatment is sometimes high. The above-described treating agents do not show sufficient performance of harm-elimination to some kinds of metal hydride gases with poor reactivity such as germane.
On the other hand, each of the chemical reactions following the above-mentioned treatment of the exhaust gases is an exothermic reaction. Accordingly, the treatment of the exhaust gases with metal compounds inevitably causes a rise in temperature, particularly when performing a treatment of the exhaust gases containing a high level of metal hydride or a treatment of a large amount of the exhaust gases, a remarkable temperature rise is likely to be caused. For which reason, the treating agent is required not only to be high-performance but also to have low exothermic property.